1. Field of the Invention
Embodiments relate to an image sensor and an image pick-up apparatus including the same.
2. Description of Related Art
With the increase in demand for high-quality image acquisition technology in an image acquisition apparatus, such as a camera, an auto focus (AF) system has been increasingly applied to cameras for mobile phones or small-sized mobile devices as well as digital cameras and an interchangeable lens cameras.
A phase difference detection type AF system or a contrast detection type AF system is mainly used as the AF system.
In the contrast detection type AF system, high frequency data are extracted from image data acquired by an image sensor, and AF control is performed to maximize the high frequency data. To this end, a signal processing circuit is required. However, an additional sensor or an optical system is not needed. Consequently, the AF system may be configured at relatively low cost. However, the contrast detection type AF system is slower and less accurate than the phase difference detection type AF system.
In the phase difference detection type AF system, light incident through a pick-up lens is pupil-divided into a pair of images, and a phase difference, which is an interval between the images, is detected to set the position of the pick-up lens, thereby detecting focus.
In the phase difference detection type AF system, a phase difference detection AF sensor may be provided separately from the pick-up lens, or phase difference detection pixels may be arranged in an image sensor.
In the phase difference detection type AF system, focus accuracy is improved as the number of phase difference detection pixels is increased. However, the phase difference detection pixels each have a narrower opening than general image detection pixels and thus have low sensitivity. As a result, image quality is deteriorated when the number of phase difference detection pixels is increased.
In order to perform accurate focus adjustment without deterioration of image quality in an AF system using phase difference detection pixels, therefore, it is necessary to properly arrange the phase difference detection pixels.